Marvin was one of the most popular names in the first half of the 20th century. Eventually it fell out of favor because it was so popular for so long that new parents wouldn't name their kids Marvin because it was seen as an "old fashioned name" popular among old people.

This is one of the main reasons names come and go in popularity. A name gets popular, those people age, there's a ton of people with it who are old, it seems like an "old person name" and falls out of favor. Names then come back around when they're unpopular and parents are looking for name that isn't super common - only to have many parents come to the same conclusion. It's why parents often think they've picked a fairly uncommon name for their kid only to later discover it was a very popular name in the years their kid was born. In the US the only names that are fairly immune to this kind of cycle are Biblical names.

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